We are studying the structures of carbohydrates on glycoproteins with a goal of understanding the relationships between protein structure and carbohydrate structure. Our systems include normal and cancer cells. Results from studies of fibroblasts and their malignant transformants indicate that changes in carbohydrate heterogeneity accompany cancer. We are attempting detailed studies on the relationship between proteins and carbohydrates by using myeloma and lymphoma cell lines producing IgM either as a cell membrane component or in soluble form. We have completed NMR studies on the major structures of carbohydrates found at each of the five glycosylation sites. We are now in the process of doing similar studies on the membrane-bound form of IgM. We are writing a computer program to facilitate analyses of signals from NMR spectra. In other studies, we are determining carbohydrate structures on IgM produced by a number of hybridoma cell lines. The very significant result that we have found is that hybridoma cell lines frequently have dramatic alterations in the antibody carbohydrates. We think that these results could have important implications for the use of hybridoma antibodies in patient treatments. We are extending these studies to include mutant cell lines which have alterations in the polypeptide chain, and determining the consequences on the carbohydrate structures at individual glycosylation sites. Finally, we are comparing rates of synthesis and subcellular pathways for membrane-bound and secreted glycoproteins. Our data show that the pathway for membrane-bound IgM is significantly different than for soluble IgM. The pathway appears to be an important determinant for the structure of oligosaccharide side chains on IgM. (A)